<!DOCTYPE html>
<html>

<head>
    <meta charset="utf-8">
    <title>不规则投影</title>
</head>
<style>
    * {
        margin: 0;
        padding: 0;
    }

    /* html,
    body {
        width: 100%;
        height: 100%;
    } */

    .box>div{
        width: 100px;
        height: 100px;
        background-color: thistle;
        margin-bottom: 10px;
        margin-left: 10px;
        position: relative;
    }

    .box>div:nth-child(1):after {
        content: "";
        border-width: 10px;
        border-style: solid;
        border-color: transparent transparent transparent thistle;
        display: inline-block;
        position: absolute;
        right: -20px;
        top: 40px;
    }
    .box>div:nth-child(2){
        background-color: #fff;
        border: 5px dashed plum;
    }
    .box>div:nth-child(3){
        background: linear-gradient(-45deg,transparent 15px,thistle 0);
    }
    .box1 {
        box-shadow: 2px 2px 4px rgba(0, 0, 0,0.5);
    }
    .box2 {
        filter: drop-shadow(2px 2px 4px rgba(0, 0, 0,0.5));
    }
</style>

<body>
    <!-- box-shadow -->
    <div class="box">
        <div class="box1">aaa
        </div>
        <div class="box box1">aaa
        </div>
        <div class="box box1">aaa
        </div>
        
    </div>
    <!-- filter -->
    <div class="box">
        <div class="box box2">aaa
        </div>
        <div class="box box2">aaa
        </div>
        <div class="box box2">aaa
        </div>
    </div>
</body>
<script type="text/javascript">
</script>

</html>